Why is Maximum RAM Memory Limited to 4 GB with a 32-bit Address Bus?

[Useful nucleus]

Why, with a 32-bit adress bus , we can only have a maximum of 4 GB RAM memory?

 

[rty640]

4GB = 2^32 bytes.

64-bit can address 2^64 bytes.

 

[Useful nucleus]

Thank you!

 

[cam875]

but remember that most CPU's in todays market support Physical Address extension along with many Operating systems. All it does is extend the address bus from 32 bits to 36 bits but is still compatible with 32 bit applications and stuff. But if needed this can extend the amount of RAM from 4GB to 64GB. Thats quite the difference.

 

[michinobu]

4GB = 2^32 bytes.

64-bit can address 2^64 bytes.

Yeah, I believe that every bit represents a sector (usually a byte) in physical memory.